A typical prosthetic leg and foot includes a socket, pylon, and foot. A socket is commonly referred to as the portion of a prosthesis that fits around and envelops a residual limb or stump, and to which prosthetic components, such as a foot, are attached. When providing a socket to an amputee, it is essential to properly fit the socket and align various parts of the prosthesis to the amputee. Fitting and alignment of the socket and the parts are difficult tasks to perform, and require extensive knowledge, training and skill for the prosthetist.
Typically, sockets for definitive prostheses are customized for a residual limb of a user. According to one method, the sockets are formed over a model of the stump, such as one formed by plaster-of-Paris, to be used to distribute forces between the socket and the stump in a comfortable way to the amputee. In another method, the socket may be obtained from computer aided design by modeling the shape of the stump, and subsequently forming a model. Once the model is obtained in either of these methods, a socket is formed over the model by using fabric and liquid plastic resin to obtain a definitive rigid socket customized to a limb.
Proper fitting of a socket to the stump is critical to the success of the prosthesis. The socket must fit closely to the stump to provide a firm connection and support, but must also be sufficiently loose to allow for circulation. In combination with proper fitting, the socket must transfer loads from the residual limb to the ground in a comfortable manner.
Most prosthetic sockets are permanently formed to a customized shape that is static, meaning the socket does not account for shape and volume fluctuations of the residual limb. When there are shape and volume fluctuations, the fitting of the socket is impeded, with these sockets causing discomfort, pain and soft tissue breakdown of the stump. Conventional sockets tend to be bulky and cumbersome to wear, and may be difficult to don making the residual limb uncomfortable when worn.
As to methods of attaching the socket to the residual limb, conventional sockets rely on different mechanisms such as negative pressure or a friction or tension based interface. Conventional sockets may have poor force distribution on the residual limb causing a concentration of pressure on a certain area of the stump. This poor distribution of pressure causes pain, discomfort, and tissue breakdown. Conventional sockets generally are not breathable which results in undesirable temperature and humidity within the socket.
For certain types of amputations such as disarticulation amputations where the limb is separated at a joint, it is difficult to create sockets which are not bulky and provide use of the natural anatomy. Conventional sockets for disarticulation amputations use a rigid socket which requires that the opening for the socket be larger than the joint to allow for donning and doffing. The rigid sockets generally have a general uniform shape which receives a large portion of the residual limb and the space between the residual limb and the interior of the rigid socket wall is filled in with a soft or cushioning material.
There is a need for an adjustable prosthetic socket that accommodates shape and volume fluctuations of the residual limb and comfortably transfers loads from the residual limb to the ground.